TWI458386B - Driving method of light emitting diode string, light emitting diode string drive circuit and method of drive thereof - Google Patents

Description

Driving method of light emitting diode string, driving circuit of light emitting diode string and driving method thereof

The present invention relates to a driving circuit and a driving method thereof, and more particularly to a driving circuit for a light emitting diode string and a driving method thereof.

A light-emitting diode is a semiconductor electronic component that is currently common to emit light. This electronic component appeared as early as the 1960s, and the light that has been developed so far has spread to visible light, infrared light, and ultraviolet light, and the luminosity has also increased to a considerable degree of luminosity. The use has also expanded to be used as an indicator light, a display panel, and a display backlight module; and with the advent of white light-emitting diodes, the use of illumination has continued to evolve.

However, with the increase in energy-saving demand, not only the requirements for improving the operational efficiency of the LEDs are increasing, but also the efficiency of the operation of the LED driving circuit is becoming more and more important, and the current-sense component IC of the driving circuit design is increasingly important. The heat loss problem is one of the directions that the technician wants to improve.

The invention provides a driving circuit for a light emitting diode array and a driving method thereof, which adopts a dual dynamic voltage feedback mechanism to control a driving voltage outputted to an array of light emitting diodes, thereby improving heat loss of the current stabilizing element IC. Further, the stability of the driving circuit of the light emitting diode array is improved.

Therefore, the driving circuit of the LED string of the present invention comprises a power supply module, a plurality of LED strings, a current controller and a reference voltage generating module. The power supply module has a first input end and a second input end and a first output end, and is configured to output a first driving voltage from the first output end according to the signal received by the first input end and the second input end. The first end of each of the LED strings is electrically coupled to the first output of the power supply module for receiving the first driving voltage. The current controller is configured to individually control the current flowing through each of the LED strings, and is electrically coupled to the first input end of the power supply module. The current controller includes a plurality of current stabilizing units, and each of the current stabilizing units corresponds to each of the light emitting diode strings. Each current stabilizing unit contains a transistor and a resistor. The transistor has a first end, a second end and a control end. The first end of the transistor is electrically coupled to the second end of the corresponding LED string, and the control end is used to control the first end to be electrically coupled or electrically isolated from the second end. One end of the resistor is electrically coupled to the second end of the transistor. The first driving voltage is used to drive to each of the light emitting diode strings, and a first voltage is separately formed at a first end of each of the transistors, and a second voltage is separately formed at a second end of each of the transistors. The current controller is further configured to selectively provide one of the first voltages or the second voltage to the first input of the power supply module. The reference voltage generating module is electrically coupled to the second input end of the power supply module and the current controller for providing a first reference voltage or a second reference voltage to the second input end of the power supply module, and if the current When the controller provides one of the plurality of first voltages to the first input terminal, the reference voltage generating module provides a first reference voltage to the second input terminal; if the current controller provides the plurality of second voltages When the first input terminal is given, the reference voltage generating module provides a second reference voltage to the second input terminal.

In addition, the driving method of the driving circuit of the LED string of the present invention includes the following steps: first, receiving a first voltage having a minimum value, and adjusting the output first driving voltage according to the first reference voltage; Comparing whether a difference between the first voltage having the minimum value and the remaining first voltage exceeds a set threshold; and when confirming that the difference is greater than or equal to the set threshold, receiving the second voltage having the minimum value and according to the The second reference voltage adjusts the output first driving voltage again.

In addition, the driving method of the LED string of the present invention is for driving a plurality of parallel LED strings, each LED string comprising a plurality of LEDs connected in series, a transistor and a resistor. The transistor includes a control end, a first end and a second end, and the driving method comprises the following steps: first, generating a first driving voltage by using a power supply module; and then providing a first driving voltage to each of the light emitting diodes The body string generates a current in each of the light emitting diode strings, wherein the current of each of the light emitting diode strings flows through the first ends of the plurality of light emitting diodes and the light emitting diode strings of the light emitting diode strings a second end of the transistor of the light-emitting diode string and a resistance of the light-emitting diode string; furthermore, the first end of the transistor of each of the light-emitting diode strings has a first voltage, and the light of the light-emitting diode string The second end of the crystal has a second voltage; then, receiving the first voltage and the second voltage of each of the LED strings; and then selectively providing the first voltage group or the second voltage group to the power supply module, First voltage group Having one of a first voltage of each of the light emitting diode strings and a first reference voltage, and the second voltage group includes one of a second voltage of each of the light emitting diode strings and a second reference voltage; After the first voltage group or the second voltage group is provided to the power supply module, the first driving voltage is adjusted according to the voltage group supplied to the power supply module.

The driving circuit of another LED string of the present invention comprises a power supply module, a plurality of LED strings, a current controller and a reference voltage generating module. The power supply module has a first input end and a second input end and a first output end, and is configured to output a first driving voltage from the first output end according to the signal received by the first input end and the second input end. The first end of each of the LED strings is electrically coupled to the first output of the power supply module for receiving the first driving voltage. The current controller is configured to individually control the current flowing through each of the LED strings, and is electrically coupled to the first input end of the power supply module. The current controller includes a plurality of current stabilizing units, and each of the current stabilizing units corresponds to each of the light emitting diode strings. Each current stabilizing unit contains a transistor and a resistor. The transistor has a first end, a second end and a control end. The first end of the transistor is electrically coupled to the second end of the corresponding LED string, and the control end is used to control the first end to be electrically coupled or electrically isolated from the second end. One end of the resistor is electrically coupled to the second end of the transistor. The first driving voltage is used to drive to each of the light emitting diode strings, and a first voltage is separately formed at a first end of each of the transistors, and a second voltage is separately formed at a second end of each of the transistors. The current controller is configured to selectively provide one of the first voltages or the second voltage to be multiplied by a predetermined ratio to the first input of the power supply module. The reference voltage generating module is electrically coupled to the second input end of the power supply module for providing a first reference voltage to the second input end of the power supply module.

The driving circuit of the further LED string of the present invention comprises a power supply module, a light emitting diode string, a current controller and a reference voltage generating module. The power supply module has a first input end and a second input end and a first output end, and is configured to output a first driving voltage from the first output end according to the signal received by the first input end and the second input end. The first end of the LED string is electrically coupled to the first output of the power supply module for receiving the first driving voltage. The current controller is configured to control a current flowing through the LED string and electrically coupled to the first input end of the power supply module. The current controller includes a current stabilizing unit. The steady flow unit includes a transistor and a resistor. The transistor has a first end, a second end and a control end. The first end of the transistor is electrically coupled to the second end of the LED string, and the control end is configured to electrically or electrically isolate the first end from the second end. One end of the resistor is electrically coupled to the second end of the transistor. The first driving voltage is used to drive the LED string, and a first voltage is formed at the first end of the transistor, and a second voltage is formed at the second end of the transistor. The current controller is further configured to provide a second voltage to the first input of the power supply module. The reference voltage generating module is electrically coupled to the second input end of the power supply module for providing a first reference voltage to the second input end of the power supply module.

In summary, the driving method of the LED string of the present invention, the driving circuit of the LED string and the driving method thereof, through the dual dynamic voltage feedback mechanism, to adjust the driving voltage output to the LED array In particular, it is possible to improve the heat loss problem of the current-sense element IC without increasing the wafer area and the construction cost of the current-sense element IC, thereby improving the stability of the driving circuit of the light-emitting diode array.

The above and other objects, features and advantages of the present invention will become more <RTIgt;

In the current driving circuit design of the LED array, in order to avoid the temperature of the current-sense element IC being too high, some driving circuits adopt a dynamic voltage feedback mechanism to reduce the voltage across the IC of the current-stabilizing element, and the dynamic voltage The feedback mechanism operates by obtaining the terminal voltage of the steady current component IC as the feedback voltage and feeding it back to the power supply module, thereby adjusting the driving voltage of the power supply module output to the LED array to achieve a reduction in stability. Heat loss problem of the flow element IC.

However, the dynamic voltage feedback mechanism described above has the following problems. For example, when all the channels in the array of LEDs operate in the saturation region, the current-sense element IC can be used as an adjustable voltage-down circuit and the excess voltage is lost in the regulator of the current-sense element IC. On the component, therefore, this method is prone to the problem of excessive heat loss. If there is no good heat dissipation mechanism, it may cause the current-sense component IC to fail or be damaged. On the other hand, because of the difference in forward voltage of the LED strings in each channel, the feedback voltage of the current-sense element IC in each channel may be higher than 0.5 volts (for example, about 0.5 volts to 2 volts), as a result, also causes a problem of excessive heat accumulation of the current stabilizing element IC.

Therefore, in order to reduce the problem of heat loss in the current stabilizing element IC, it can be realized by reducing the feedback reference level. In the current common drive circuit design, the minimum feedback voltage of the current-stabilizing component IC in each channel can reach about 0.5 volts, but if the current circuit architecture is to reduce the minimum feedback voltage to less than 0.5 volts, it is needed. The die size of the current stabilizing element IC must be increased, which will result in an increase in the cost of building the current stabilizing element IC. The driving circuit of the LED array of the present invention and the driving method thereof, through the dual dynamic voltage feedback mechanism, adjust the driving voltage outputted to the LED array, in particular, it is not necessary to increase the wafer area of the current stabilizing element IC. With the cost of construction, the heat loss problem of the current-sense element IC can be improved, and the stability of the driving circuit of the light-emitting diode array can be improved. The specific implementation is as follows.

Please refer to FIG. 1. FIG. 1 is a block diagram of a circuit according to an embodiment of the present invention. As shown in FIG. 1 , the driving circuit 100 of the LED array of the embodiment of the present invention includes a power supply module 10 , a light emitting diode array 20 , a current controller 30 , and a reference voltage generating module 40 .

The power supply module 10 has a first input terminal F1, a second input terminal F2 and a first output terminal O1. The power supply module 10, such as a DC power supply module, can convert the received input voltage Vin to output a first driving voltage Vled. The power supply module 10 further adjusts the first driving voltage Vled from the first output terminal according to the signal received by the first input terminal F1 and the second input terminal F2. In addition, the power supply module 10 can also be, for example, a DC to DC converter, a switched DC to DC converter, an AC to DC converter, and other power generators having a power conversion function. The power supply module 10 is, for example, a closed-loop controlled switching DC-to-DC converter for adjusting the first output according to the feedback voltage received by the first input terminal F1 and the reference voltage received by the second input terminal F2. The voltage of O1, in turn, enables the feedback voltage received by the first input terminal F1 to be maintained within a predetermined range.

The LED array 20 is electrically coupled to the first output end O1 of the power supply module 10 . The LED array 20 includes a plurality of LED strings L1, L2, L3~Ln, but not limited thereto, and only one LED string. Each of the light emitting diode strings is composed of a plurality of light emitting diodes in series. Specifically, the first ends (eg, the positive input ends) of the LED strings L1, L2, L3, and Ln are respectively electrically coupled to the first output end O1 of the power supply module 10 to receive the first driving voltage. Vled.

The current controller 30 is electrically coupled to the second end of the LED string L1, L2, L3~Ln relative to the first end (eg, the negative input terminal) and the first input terminal F1 of the power supply module 10 . The current controller 30 is used to individually control the current flowing through the LED strings L1, L2, L3~Ln. The current controller 30 includes a current stabilizing unit S1, S2, S3~Sn and a selection module 40. The number of the current stabilizing units may correspond to the number of light emitting diode strings.

Each of the current stabilizing units S1, S2, and S3 to Sn is electrically coupled to the second end of each of the LED strings. The current stabilizing units S1, S2, S3 to Sn include transistors Q1, Q2, Q3 to Qn and resistors R1, R2, R3 to Rn. For example, the current stabilizing unit S1 includes a transistor Q1 and a resistor R1. The transistor Q1 has a first end (eg, a 汲 extreme), a second end (eg, a source terminal), and a control terminal (eg, a gate terminal). The first end of the transistor Q1 is electrically coupled to the second end of the corresponding LED string L1. The control end of the transistor Q1 is used to control the first end to be electrically coupled or electrically isolated from the second end. One end of the resistor R1 is electrically coupled to the second end of the transistor Q1. The other end of the resistor R1 is grounded. In addition, the architectures of the other steady current units S2, S3~Sn are similar, and will not be described below.

As described above, the first driving voltage Vled is used to drive the LED strings L1, L2, L3~Ln, and form a first voltage (Ch1_Vcs, Ch2_Vcs, Ch3_Vcs~Chn_Vcs) at the first end of each transistor, And forming a second voltage (Ch1_Rsens, Ch2_Rsens, Ch3_Rsens~Chn_Rsens) individually at the second end of each of the transistors. The current controller 30 is configured to selectively supply the first voltage or the second voltage to the first input terminal F1 of the power supply module 10.

Specifically, the selection module 34 is electrically coupled to the first ends of the transistors Q1, Q2, Q3~Qn in each of the LED strings L1, L2, L3~Ln, and is selected to have the smallest A light-emitting diode string of a voltage (i.e., a terminal voltage corresponding to the first end of the transistors Q1, Q2, Q3 - Qn). Thereby, the current controller 30 can provide a minimum first voltage of the first voltages or a second voltage of the LED strings having the smallest first voltage (ie, corresponding to the transistors Q1, Q2, Q3~) The terminal voltage of the second end of Qn is supplied to the first input terminal F1 of the power supply module 10. For example, if the first voltage Ch1_Vcs of the LED string L1 is the smallest of all the LED strings L1, L2, L3~Ln, the current controller 30 provides the first voltage of the LED string L1. The second voltage Ch1_Rsens of the Ch1_Vcs or the LED string L1 is supplied to the first input terminal F1 of the power supply module 10. Of course, if there is only a single LED string, the LED string having the smallest first voltage is defined as the single LED string. In addition, the selection module 34 can be implemented using an integrated circuit such as an Application-specific Integrated Circuit (ASIC), a Field Programmable Logic Gate Array (FPGA), or a Microcontroller (MCU).

The reference voltage generating module 40 is electrically coupled to the current controller 30 and the second input terminal F2 of the power supply module 10, respectively. The reference voltage generating module 40 is configured to provide a first reference voltage Vref1 or a second reference voltage Vref2 to the second input terminal F2. In addition, when the current controller 30 provides one of the plurality of first voltages to the first input terminal F1, the reference voltage generating module 40 provides the first reference voltage Vref1 to the second input terminal F2. When the current controller 30 provides one of the plurality of second voltages to the first input terminal F1, the reference voltage generating module 40 provides the second reference voltage Vref2 to the second input terminal F2. For example, if the first voltage Ch1_Vcs of the LED string L1 is the smallest of all the LED strings L1, L2, L3~Ln, the current controller 30 provides the first voltage of the LED string L1. The second voltage Ch1_Rsens of the Ch1_Vcs or the LED string L1 is supplied to the first input terminal F1 of the power supply module 10. When the current controller 30 provides the first voltage Ch1_Vcs of the LED string L1 to the first input terminal F1 of the power supply module 10, the reference voltage generating module 40 provides the first reference voltage Vref1 to the second input terminal F2. . When the current controller 30 provides the second voltage Ch1_Rsens of the LED string L1 to the first input terminal F1 of the power supply module 10, the reference voltage generating module 40 provides the second reference voltage Vref2 to the second input terminal F2.

Please refer to FIG. 2. FIG. 2 is a schematic circuit diagram of a light-emitting diode array and a current stabilizing unit according to an embodiment of the present invention. As shown in FIG. 2, the LED array 20 of the embodiment of the present invention is composed of a plurality of LED strings L1, L2, and L3 to Ln connected in parallel with each other. The steady current units S1, S2, S3~Sn include transistors Q1, Q2, Q3~Qn and resistors R1, R2, R3~Rn, and the architectures of the current stabilizing units S1, S2, S3~Sn have been described as before. This will not be repeated here. The transistors Q1, Q2, Q3 to Qn may be, for example, a bipolar junction transistor (BJT) or a field effect transistor (FET). The resistors R1, R2, R3~Rn are generally used to convert the currents flowing through the LED strings L1, L2, L3~Ln into corresponding voltages, and the current controller 30 generates PWM signals according to the voltage to control The switches of the transistors Q1, Q2, Q3~Qn further achieve the effect of stabilizing the current.

The driving current Iled_1 is generated by the voltage of the first driving voltage Vled. After the driving current Iled_1 flows through the LED string L1, the first end of the transistor Q1 is formed with a first voltage Ch1_Vcs at the second end of the transistor Q1. A second voltage Ch1_Rsens is formed. Similarly, after the driving current Iled_2 flows through the LED string L2, the first end of the transistor Q2 is formed with a first voltage Ch2_Vcs, and the second end of the transistor Q2 is formed with a second voltage Ch2_Rsens. Similarly, after the driving current Iled_3 flows through the LED string L3, the first end of the transistor Q3 is formed with a first voltage Ch3_Vcs, and the second end of the transistor Q3 is formed with a second voltage Ch3_Rsens. After the driving current Iled_n flows through the LED string Ln, a first voltage Chn_Vcs is formed at the first end of the transistor Qn, and a second voltage Chn_Rsens is formed at the second end of the transistor Qn. The first voltages Ch1_Vcs, Ch2_Vcs, Ch3_Vcs~Chn_Vcs, and the second voltages Ch1_Rcss, Ch2_Rsens, Ch3_Rsens~Chn_Rsens are respectively supplied to the selection module 34 (as shown in FIG. 3).

Next, please refer to FIG. 3. FIG. 3 is a schematic circuit diagram of a selection module, a reference voltage generation module, and a power supply module according to an embodiment of the present invention. As shown in FIG. 3, the selection module 34 receives the first voltages Ch1_Vcs, Ch2_Vcs, Ch3_Vcs~Chn_Vcs, and the second voltages Ch1_Rsens, Ch2_Rsens, Ch3_Rsens~Chn_Rsens, respectively.

The selection module 34 includes a minimum value selector 342, a first multiplexer 344, a second multiplexer 346, and a comparator 348.

The minimum value selector 342 is electrically coupled to the first ends of the transistors Q1, Q2, Q3 - Qn in the LED strings L1, L2, L3 - Ln to receive the first voltages Ch1_Vcs, Ch2_Vcs, Ch3_Vcs~Chn_Vcs, and outputs a first voltage having a minimum value to the first multiplexer 344, and outputs a first control signal CS_1 to a second multiplexer 346.

The first multiplexer 344 is electrically coupled to the output of the minimum selector 342, the output of the second multiplexer 346, and the first input F1 of the power supply module 10. The first multiplexer 344 receives the first voltage having the minimum value and the second voltage having the minimum value, and is controlled by the second control signal CS_2 to select to output the first voltage having the minimum value or the second voltage having the minimum value. . For example, when the second control signal CS_2 is at a low level, the first voltage having the minimum value is output to the first input terminal F1 of the power supply module 10. When the second control signal CS_2 is at a high level, a second voltage having a minimum value is output to the first input terminal F1 of the power supply module 10.

The second multiplexer 346 is electrically coupled to the second ends of the transistors Q1, Q2, Q3~Qn in the LED strings L1, L2, L3~Ln, and the input ends of the first multiplexer 344, respectively. The output of the minimum selector 342. The second multiplexer 346 is configured to receive the second voltages Ch1_Rsens, Ch2_Rsens, Ch3_Rsens~Chn_Rsens, and the first control signal CS_1, and output the LED string having the first voltage of the minimum value according to the first control signal CS_1. The second voltage is applied to the first multiplexer 344.

The comparators 348 are electrically coupled to the first multiplexer 344 and the reference voltage generating module 40, respectively. The comparator 348 respectively receives the set threshold value and the first voltage difference, thereby comparing whether the first voltage difference between the LED string having the smallest first voltage and the LED string having the second smallest voltage exceeds The threshold value is set, and the second control signal CS_2 is supplied to the reference voltage generating module 40 and the first multiplexer 344. For example, when the first voltage difference is greater than or equal to the set threshold, the second control signal CS_2 having a high level is output. When the first voltage difference is less than the set threshold, the second control signal CS_2 having a low level is output. For example, the first voltage difference is, for example, the value of the second voltage that is the second smallest minus the minimum voltage.

The reference voltage generation module 40 includes a third multiplexer 402. The third multiplexer is electrically coupled to the comparator 348 and the second input terminal F2 of the power supply module 10, respectively. The third multiplexer 402 determines to output the first reference voltage Vref1 or the second reference voltage Vref2 according to the second control signal CS_2. For example, when the second control signal CS_2 is at a high level, the third multiplexer 402 outputs the second reference voltage Vref2 to the second input terminal F2 of the power supply module 10. When the second control signal CS_2 is at a low level, the output third multiplexer 402 outputs the first reference voltage Vref1 to the second input terminal F2 of the power supply module 10. Wherein the first reference voltage Vref1 is generally greater than the second reference voltage Vref2.

Please refer to FIG. 8. Referring to FIG. 8, FIG. 8 is a circuit block diagram of another embodiment of the present invention. As shown in FIG. 8, the driving circuit 100 of the LED array of the embodiment of the present invention includes a power supply module 10, a light emitting diode array 20, a current controller 30, and a reference voltage generating module 40. Different from FIG. 1 , in the embodiment of FIG. 8 , the electrical coupling relationship between the reference voltage generating module 40 and the current controller 30 is not necessary, but the embodiment is not intended to limit the present invention. For the details of the components of the LED array 20 and the current stabilizing units S1, S2, and S3 to Sn in FIG. 8, please refer to FIG.

Referring to FIG. 9 and FIG. 8 , FIG. 9 is a schematic circuit diagram of a selection module, a reference voltage generation module, and a power supply module according to another embodiment of the present invention, which is different from the embodiment shown in FIG. 3 . A multiplexer 344 is electrically coupled to the output of the minimum selector 342, the first input F1 of the power supply module 10, and is electrically coupled to the output of the second multiplexer 346 via the multiplier 347. . In other words, unlike the embodiment shown in FIG. 3, the first multiplexer 344 receives one of the second voltages (Ch1_Rsens, Ch2_Rsens, Ch3_Rsens~Chn_Rsens) multiplied by a predetermined multiplying factor K, and passes through the first multiplexer 344. One of the first voltages Ch1_Vcs, Ch2_Vcs, Ch3_Vcs~Chn_Vcs or one of the second voltages Ch1_Rsens, Ch2_Rsens, Ch3_Rsens~Chn_Rsens is selected to be multiplied by a preset magnification K to the first input terminal F1 of the power supply module 10.

In addition, another embodiment of FIG. 9 is different from FIG. 3 in that the voltage generating module 40 can supply only the first reference voltage Vref1 to the power supply module 10. In this embodiment, the power supply module 10 is still based on the feedback voltage received by the first input terminal F1 and the reference voltage received by the second input terminal F2 to adjust the voltage of the first output terminal O1, thereby making the first input The feedback voltage received by terminal F1 can be maintained within a predetermined range. However, in this embodiment, only the first reference voltage Vref1 is required to be supplied to the power supply module 10, because before the first voltage F1_Rsens, Ch2_Rsens, Ch3_Rsens~Chn_Rsens is supplied to the first input terminal F1, One of the two voltages Ch1_Rsens, Ch2_Rsens, Ch3_Rsens~Chn_Rsens has been multiplied by a magnification K, enabling it to use the first reference voltage Vref1 as a reference value. For example, when one of the first voltages (eg, about 0.5 volts) is supplied to the first input terminal F1, the first reference voltage Vref1 may be, for example, 0.5 volts, and if it is turned to provide a second voltage (eg, approximately 0.1 volts) When one of the first input terminals F1 is given, it must be switched to use the second reference voltage Vref2, for example, 0.1 volts is supplied to the second input terminal. However, in this embodiment, one of the second voltages (for example, about 0.1 volts) may be supplied by a predetermined multiple K (in this example, 5 times) to the first input terminal F1 of the power supply module 10. The first reference voltage Vref1 (for example, 0.5 volts) may be used as the reference voltage of the power supply module 10.

Next, please refer to FIG. 1 and FIG. 4 together. FIG. 4 is a flow chart showing the steps of the driving method of the LED array according to the embodiment of the present invention. As shown in FIG. 4, first, in step S401, the power supply module 10 receives the first voltage having the minimum value output by the current controller 30, and the power supply module 10 outputs the first output according to the reference voltage generating module 40. A reference voltage Vref1 adjusts the first driving voltage Vled output from the power supply module 10 to the LED array 20.

Next, in step S403, the current controller 30 compares whether the difference between the first voltage having the minimum value and the remaining first voltage exceeds a set threshold (S403) to output the comparison result to the power supply module 10 and the reference. Voltage generation module 40. Specifically, in step S403, the current controller 30 compares the first voltage having the smallest value with the first voltage having the second smallest value. For example, if the first voltage includes 0.5 volts, 0.3 volts, 0.4 volts, 0.6 volts, and 0.8 volts, the current controller 30 compares whether the difference between 0.3 volts and 0.4 volts exceeds a set threshold. In addition, in step S403, when the current controller 30 confirms that the difference is less than the set threshold, the process returns to step S401, and the power supply module 10 adjusts the output according to the first reference voltage Vref1. A driving voltage Vled.

In step S405, when the current controller 30 confirms that the difference is greater than or equal to the set threshold, the power supply module 10 receives the second voltage having the minimum value output by the current controller 30, and the power source The supply module 10 re-adjusts the first driving voltage Vled output from the power supply module 10 to the LED array 20 according to the second reference voltage Vref2 output by the reference voltage generating module 40.

5 and FIG. 6, FIG. 5 is a block diagram of another embodiment of the present invention, and FIG. 6 is a flow chart showing the steps of driving the LED string according to another embodiment of the present invention. Another embodiment of the present invention can be used to drive a plurality of parallel LED strings L1, L2, L3~Ln, and each of the LED strings L1, L2, L3~Ln includes a plurality of LEDs D1 connected in series. D2, D3~Dn, transistors Q1, Q2, Q3~Qn and resistors R1, R2, R3~Rn, the transistors Q1, Q2, Q3~Qn comprise a control end, a first end and a second end. The power supply module 10 can convert the received input voltage Vin to output a first driving voltage Vled. The power supply module 10 further adjusts the first driving voltage Vled from the first output terminal according to the signal received by the first input terminal F1 and the second input terminal F2, which is different from the embodiment of FIG. An input terminal F1 is configured to receive the first voltage group, wherein the first voltage group is the smallest first voltage of the LED strings L1, L2, L3~Ln and the first reference voltage Vref1, and the second input terminal F2 is And a second voltage group for receiving the second voltage group, wherein the light emitting diode string L1, L2, L3 L Ln has the smallest first voltage and the second reference voltage Vref2. The power supply module 10 adjusts the first output terminal to output the first driving voltage Vled according to the first voltage group or the second voltage group.

Referring to FIG. 6, first, in step S601, the first driving voltage Vled is generated using the power supply module 10.

Next, in step S603, a first driving voltage Vled is supplied to each of the LED strings L1, L2, L3~Ln to generate a current in each of the LED strings L1, L2, L3~Ln, wherein each The currents of the LED strings L1, L2, L3~Ln flow through the complex LEDs L1, D2, D3~Dn, and the LED string L1 of the LED strings L1, L2, L3~Ln. The first ends of the transistors Q1, Q2, Q3~Qn of L2, L3~Ln, the second ends of the transistors Q1, Q2, Q3~Qn of the LED strings L1, L2, L3~Ln and the second light emitting The resistors R1, R2, R3 to Rn of the polar body strings L1, L2, and L3 to Ln. In addition, the first ends of the transistors Q1, Q2, Q3~Qn of each of the LED strings L1, L2, L3~Ln have a first voltage, and each of the LED strings L1, L2, L3~Ln The second ends of the transistors Q1, Q2, Q3~Qn have a second voltage.

Then, in step S605, the first voltage and the second voltage of each of the LED strings L1, L2, L3 to Ln are received.

Next, in step S607, the first voltage group or the second voltage group is selectively supplied to the power supply module 10, wherein the first voltage group includes the LED strings L1, L2, L3~Ln One of the first voltages and the first reference voltage Vref1, and the second voltage group includes one of the second voltages of the photodiode strings L1, L2, L3~Ln and the second reference voltage Vref2. Specifically, a minimum of the first voltages of each of the light emitting diode strings L1, L2, L3 to Ln and the first reference voltage Vref1 are provided, or a second voltage of the light emitting diode string having the smallest first voltage is provided. And the second reference voltage Vref2 is supplied to the power supply module 10. In addition, if the difference between the minimum value of the first voltage and the second smallest value of the first voltage is less than a preset threshold, the first voltage group is supplied to the power supply module 10; if the minimum value of the first voltage is the first The difference between the second smallest value of the voltage is greater than or equal to the threshold value, and the second voltage group is supplied to the power supply module 10.

Then, in step S609, after the first voltage group or the second voltage group is selectively supplied to the power supply module 10, if the first voltage group is supplied to the power supply module 10, according to the first voltage group The first driving voltage Vled is adjusted, and if the second voltage group is supplied to the power supply module, the first driving voltage Vled is adjusted according to the second voltage group. In short, after the first voltage group or the second voltage group is selectively supplied to the power supply module in step S609, the first driving voltage Vled is adjusted according to the voltage group supplied to the power supply module.

In summary, by using the second voltage (Ch1_Rsens, Ch2_Rsens, Ch3_Rsens~Chn_Rsens) as the feedback voltage to the power supply module 10, the LED strings L1, L2, L3~Ln can be made. The voltage difference between the first terminal and the second terminal of the transistors Q1, Q2, Q3 to Qn is lowered, so that the power consumption of the current controller 30 can be reduced.

For example, when the transistors Q1, Q2, Q3~Qn are field effect transistors, please refer to FIG. 7. FIG. 7 is a schematic diagram of a working point of a current controller transistor according to an embodiment of the present invention. The horizontal axis is the voltage difference between the first end and the second end of the transistor, the vertical axis is the current flowing through the transistor, and the end of the curve indicates the voltage difference between the control end of the transistor and the second end. When the first voltage (Ch1_Vcs, Ch2_Vcs, Ch3_Vcs~Chn_Vcs) is used as the feedback signal, the transistors Q1, Q2, and Q3 operate at the operating point ch1, the operating point ch2, and the operating point ch3, respectively; and when the lowest first voltage (ie, electricity) When the first voltage of the crystal Q1 and the second lowest voltage (ie, the first voltage of the transistor Q2) are greater than the set threshold, the second voltage (Ch1_Rsens, Ch2_Rsens, Ch3_Rsens~Chn_Rsens) is used as the feedback signal. The transistors Q1, Q2, and Q3 can be respectively operated at the operating point ch1', the operating point ch2', and the operating point ch3'. At this time, the transistors Q1, Q2, and Q3 in the LED strings L1, L2, L3 to Ln Some of the transistors in ~Qn may operate in the saturation region. In this example, transistors Q2 and Q3 operate in the linear region, and transistor Q1 operates in the saturation region. Therefore, the first and second terminals of transistor Q1 are operated. The difference is lower when operating in the linear region, and since the first driving voltage Vled is lower at this time, the voltage difference between the first terminal and the second terminal of the transistors Q2 and Q3 can also be lowered, and due to the transistors Q1, Q2, Q3 The voltage difference between the first end and the second end is reduced, so the power consumption (ie, the current flowing) In the voltage difference across) can be reduced, and thus all the light emitting diode strings L1, L2, L3 ~ Ln power driving circuit. In addition, the embodiment of the present invention converts to the second voltage when the lowest first voltage (ie, the first voltage of the transistor Q1) and the second lowest voltage (ie, the first voltage of the transistor Q2) are greater than the set threshold. (Ch1_Rsens, Ch2_Rsens, Ch3_Rsens~Chn_Rsens) is used as the feedback signal, so that the problem that the current is excessively large due to excessive operation of the transistor in the saturation region can be avoided. Of course, the additional judgment formula of the embodiment of the present invention is not intended to limit the present invention.

In addition, the present invention further provides a method for saving power consumption of a driving circuit when moving a single LED string L1. As disclosed in the above embodiments, the difference is that when only a single LED string L1 is driven, no further selection is provided. A voltage Ch1_Vcs or a second voltage Ch1_Rsens is supplied to the power supply module 10, and the second voltage Ch1_Rsens can be directly supplied to the power supply module 10, and the transistor Q1 corresponding to the initial LED string L1 is operated in the saturation region, so Referring to Figure 7, when operating in the saturation region, the transistor Q1 power consumption will be smaller than when operating in the linear region.

In summary, the driving method of the LED string of the present invention, the driving circuit of the LED string and the driving method thereof, through the dual dynamic voltage feedback mechanism, to adjust the driving voltage output to the LED array In particular, it is possible to improve the heat loss problem of the current-sense element IC without increasing the wafer area and the construction cost of the current-sense element IC, thereby improving the stability of the driving circuit of the light-emitting diode array.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention, and the present invention may be modified and modified without departing from the spirit and scope of the invention. The scope is subject to the definition of the scope of the patent application attached.

10. . . Power supply module

100. . . Driving circuit of light emitting diode array

110. . . Driving circuit of LED string

20. . . Light-emitting diode array

30. . . Current controller

34. . . Selection module

342. . . Minimum selector

344. . . First multiplexer

346. . . Second multiplexer

347. . . Multiplier

348. . . Comparators

40. . . Reference voltage generation module

Ch1. . . Working point

Ch1’. . . Working point

Ch2. . . Working point

Ch2’. . . Working point

Ch3. . . Working point

Ch3’. . . Working point

Ch1_Vcs. . . First voltage

Ch2_Vcs. . . First voltage

Ch3_Vcs. . . First voltage

Chn_Vcs. . . First voltage

Ch1_Rsens. . . Second voltage

Ch2_Rsens. . . Second voltage

Ch3_Rsens. . . Second voltage

Chn_Rsens. . . Second voltage

CS_1. . . First control signal

CS_2. . . Second control signal

D1. . . Light-emitting diode

D2. . . Light-emitting diode

D3. . . Light-emitting diode

Dn. . . Light-emitting diode

F1. . . First input

F2. . . Second input

Iled_1. . . Current

Iled_2. . . Current

Iled_3. . . Current

Iled_n. . . Current

L1. . . Light-emitting diode string

L2. . . Light-emitting diode string

L3. . . Light-emitting diode string

Ln. . . Light-emitting diode string

O1. . . First output

PWM. . . Pulse width modulation signal

Q1. . . Transistor

Q2. . . Transistor

Q3. . . Transistor

Qn. . . Transistor

R1. . . resistance

R2. . . resistance

R3. . . resistance

Rn. . . resistance

S1. . . Steady flow unit

S2. . . Steady flow unit

S3. . . Steady flow unit

Sn. . . Steady flow unit

Vin. . . Input voltage

Vled. . . First drive voltage

S401~S405. . . Method step description

S601~S605. . . Method step description

FIG. 1 is a block diagram of a circuit according to an embodiment of the present invention.

FIG. 2 is a schematic circuit diagram of an LED array and a current stabilizing unit according to an embodiment of the invention.

3 is a circuit diagram of a selection module, a reference voltage generation module, and a power supply module according to an embodiment of the present invention.

FIG. 4 is a flow chart showing the steps of a method for driving a light emitting diode array according to an embodiment of the invention.

FIG. 5 is a block diagram of a circuit according to another embodiment of the present invention.

FIG. 6 is a flow chart showing the steps of a driving method according to another embodiment of the present invention.

FIG. 7 is a schematic diagram of a working point of a transistor of a current controller according to an embodiment of the present invention.

Figure 8 is a block diagram of another embodiment of the present invention.

FIG. 9 is a schematic circuit diagram of a selection module, a reference voltage generation module, and a power supply module according to another embodiment of the present invention.

10. . . Power supply module

100. . . Driving circuit of light emitting diode array

20. . . Light-emitting diode array

30. . . Current controller

34. . . Selection module

40. . . Reference voltage generation module

F1. . . First input

F2. . . Second input

L1. . . Light-emitting diode string

L2. . . Light-emitting diode string

L3. . . Light-emitting diode string

Ln. . . Light-emitting diode string

O1. . . First output

Q1. . . Transistor

Q2. . . Transistor

Q3. . . Transistor

Qn. . . Transistor

R1. . . resistance

R2. . . resistance

R3. . . resistance

Rn. . . resistance

S1. . . Steady flow unit

S2. . . Steady flow unit

S3. . . Steady flow unit

Sn. . . Steady flow unit

Vin. . . Input voltage

Vled. . . First drive voltage

Claims (13)

A driving circuit for a light emitting diode string, comprising: a power supply module having a first input end and a second input end and a first output end, and configured to be based on the first input end and the second input a first driving voltage is outputted by the first output terminal; a plurality of LED strings, and the first end of each LED string is electrically coupled to the first power supply module The output terminal is configured to receive the first driving voltage; a current controller is configured to individually control a current flowing through each of the LED strings, and is electrically coupled to the first input end of the power supply module, the current The controller includes a plurality of current stabilizing units, each of which corresponds to one of the light emitting diode strings, each of the current stabilizing units comprising: a transistor having a first end and a second end a control end, the first end of the transistor is electrically coupled to the second end of the corresponding LED string, and the control end is configured to control the first end to be electrically coupled or electrically connected to the second end And a resistor, one end of the resistor is electrically coupled to the transistor The first driving voltage is used to drive the LED strings, and a first voltage is separately formed at the first end of each transistor, and is formed at the second end of each transistor. a second voltage; the current controller is configured to selectively provide one of the first voltages or one of the second voltages to the first input end of the power supply module; and a reference voltage generating mode The second input end of the power supply module and the current controller are configured to provide a first reference voltage or a second reference voltage to the second input terminal, and if the current controller provides When the first voltage is supplied to the first input terminal, the reference voltage generating module provides the first reference voltage to the second input terminal, and if the current controller provides one of the second voltages The first voltage input module provides the second reference voltage to the second input terminal. The driving circuit of the LED array of claim 1, wherein the current controller further comprises a selection module electrically coupled to the first end of the transistor of each of the LED strings. For selecting a light emitting diode string having a minimum first voltage, the current controller providing a minimum first voltage of the first voltages or a light emitting diode string having the smallest first voltage Two voltages are applied to the first input. The driving circuit of the LED array of claim 2, wherein the selection module is further configured to compare the first voltage of the LED string having the smallest first voltage with the second voltage having the second smallest Whether the difference between the first voltages of the LED strings exceeds a set threshold to determine whether the current controller provides the first voltage of the LED string having the smallest first voltage or has the smallest first A second voltage of the voltage LED string is applied to the first input. The driving circuit of the LED array of claim 1, wherein the selection module comprises: a minimum value selector, receiving the first voltage of each of the LED strings and outputting the minimum value a first voltage and a first control signal; and a first multiplexer electrically coupled to the output of the minimum selector, the first multiplexer receiving the first voltage having a minimum value and having a minimum The second voltage of the value is controlled by a second control signal to output the first voltage having a minimum value or the second voltage having a minimum value; a second multiplexer electrically coupled to the first voltage a multiplexer and an output of the minimum selector, the second multiplexer for receiving a second voltage of each of the LED strings and the first control signal to output a first voltage having a minimum value a second voltage of the diode string is coupled to the first multiplexer; and a comparator electrically coupled to the reference voltage generating module and the first multiplexer, the comparator is configured to compare the smallest a voltage LED string with a second smallest The first voltage difference of the first voltage LED string exceeds the set threshold, and the second control signal is provided to the reference voltage generating module and the first multiplexer. A driving method of a driving circuit of a light emitting diode string, comprising the steps of: receiving a first voltage having a minimum value, and adjusting an output first driving voltage according to a first reference voltage; comparing the first value having a minimum value Whether a difference between the voltage and the remaining first voltages exceeds a set threshold; and when the difference is greater than or equal to the set threshold, receiving a second voltage having a minimum value and according to a second reference The voltage again adjusts the output of the first driving voltage. The driving method of the LED array driving circuit of claim 5, wherein when the difference is less than the set threshold, the output of the first driving voltage is adjusted according to the first reference voltage. . The driving method of the LED array driving circuit of claim 5, wherein comparing whether the difference between the first voltage having the minimum value and the remaining first voltages exceeds a set threshold In the step, the first voltage having the smallest value and the first voltage having the second smallest value are compared. A driving method of a light emitting diode string for driving a plurality of parallel light emitting diode strings, each light emitting diode string comprising a plurality of light emitting diodes connected in series, a transistor and a resistor, the transistor comprising a control terminal, a first terminal and a second terminal, the driving method comprising the steps of: generating a first driving voltage by using a power supply module; and providing the first driving voltage to each of the LED strings Generating a current in each of the light emitting diode strings, wherein the current of each of the light emitting diode strings sequentially flows through the plurality of light emitting diodes of the light emitting diode string, and the first of the transistors of the light emitting diode string a second end of the transistor of the light emitting diode string and a resistance of the light emitting diode string; further a first end of the transistor of each light emitting diode string has a first voltage, the light emitting diode The second end of the transistor of the body string has a second voltage; receiving the first voltage and the second voltage of each of the LED strings; selectively providing a first voltage group or a second voltage group to the power source Supply module, wherein the first voltage group And a first reference voltage including the first voltage of the light emitting diode strings, the second voltage group comprising one of the second voltages of the light emitting diode strings and a second reference voltage; After selectively providing a first voltage group or a second voltage group to the power supply module, the first driving voltage is adjusted according to a voltage group supplied to the power supply module. The driving method of claim 8, wherein the step of selectively providing the first voltage group or the second voltage group to the power supply module is to selectively provide the light emitting diode strings. The smallest one of the first voltages and the second reference voltage of the first reference voltage or the LED string and the second reference voltage are supplied to the power supply module. The driving method of claim 8, wherein the step of selectively providing the first voltage group or the second voltage group to the power supply module is to selectively provide the light emitting diode strings. The minimum of the first voltage and the first reference voltage or the second voltage of the LED string having the smallest first voltage and the second reference voltage are supplied to the power supply module. The driving method of claim 8, wherein the step of selectively providing the first voltage group or the second voltage group to the power supply module is a minimum value of the first voltage and the first Providing the first voltage group to the power supply module if the difference between the second small value of the voltage is less than a threshold value; if the difference between the minimum value of the first voltage and the second small value of the first voltage is greater than or Equal to the threshold, the second voltage group is provided to the power supply module. A driving circuit for a light emitting diode string, comprising: a power supply module having a first input end and a second input end and a first output end, and configured to be based on the first input end and the second input a first driving voltage is outputted by the first output terminal; a plurality of LED strings, and the first end of each LED string is electrically coupled to the first power supply module The output terminal is configured to receive the first driving voltage; a current controller is configured to individually control a current flowing through each of the LED strings, and is electrically coupled to the first input end of the power supply module, the current The controller includes a plurality of current stabilizing units, each of which corresponds to one of the light emitting diode strings, each of the current stabilizing units comprising: a transistor having a first end and a second end a control end, the first end of the transistor is electrically coupled to the second end of the corresponding LED string, and the control end is configured to control the first end to be electrically coupled or electrically connected to the second end And a resistor, one end of the resistor is electrically coupled to the transistor The first driving voltage is used to drive the LED strings, and a first voltage is separately formed at the first end of each transistor, and is formed at the second end of each transistor. a second voltage; the current controller is configured to selectively provide one of the first voltages or one of the second voltages by a predetermined ratio to a first input end of the power supply module; And a reference voltage generating module electrically coupled to the second input end of the power supply module for providing a first reference voltage to the second input end. A driving circuit for a light emitting diode string, comprising: a power supply module having a first input end and a second input end and a first output end, and configured to be based on the first input end and the second input a first driving voltage is outputted by the first output terminal; a light emitting diode string, the first end of the light emitting diode string is electrically coupled to the first output of the power supply module The terminal is configured to receive the first driving voltage, and a current controller is configured to control a current flowing through the LED string and electrically coupled to the first input end of the power supply module, where the current controller includes And a current stabilizing unit comprising: a transistor having a first end, a second end and a control end, wherein the first end of the transistor is electrically coupled to the second of the LED string The control end is configured to electrically or electrically isolate the first end from the second end, and a resistor electrically coupled to the second end of the transistor; wherein a first driving voltage is used to drive the LED string and in the transistor Forming a first voltage at one end and forming a second voltage at the second end of the transistor; the current controller is configured to provide the second voltage to the first input end of the power supply module; and a reference voltage generating mode The second input end of the power supply module is electrically coupled to the second input end.